A copper alloy wiring film is used as a wiring film of a flat panel display such as a liquid crystal display, a plasma display, an organic EL display, and an inorganic EL display, and for example, a liquid crystal display device is known in which a copper alloy wiring film containing 1 to 5 atom % of Mg, and Cu and inevitable impurities as the balance is formed (see Patent Document 1).
Furthermore, a copper alloy wiring film, which contains either one of 1 atom % or less of Al, 0.5 atom % or less of Si, 2 atom % or less of Be, 2 atom % or less of Cr, 2 atom % or less of Mg, 0.5 atom % or less of Sn, 4 atom % or less of Zn, and 2 atom % or less of Ce, as an addition element, is known to have excellent migration resistance. It is also known that the copper alloy wiring film is formed by sputtering using a target containing the same components as the copper alloy wiring film (see Patent Document 2).
The copper alloy wiring film in the flat panel display is formed on a glass substrate by sputtering, and then the film is subjected to a heat treatment. When the heat treatment is performed, the addition element included in the copper alloy wiring film becomes an oxide and is moved to a front surface and a rear surface of the copper alloy wiring film. Thereby, oxide layers of the addition element are formed in the front surface and the rear surface of the copper alloy wiring film. The formed oxide layer of the addition element prevents Si or the like, which is a basic component of the glass substrate, from diffusing and penetrating into the copper alloy wiring film; and thereby, an increase in the resistivity of the copper alloy wiring film is inhibited. In addition, the formed oxide layer of the addition element improves the adhesion property of the copper alloy wiring film relative to the glass substrate.